Thermostat for engine cooling system

ABSTRACT

A thermostat for an engine cooling system, which is arranged between an engine and a radiator may include a housing having a coolant inlet through which coolant flows in from the engine and an outlet leading the coolant to the radiator; and a main valve provided in the housing and coupled to one side of wax to open or close the outlet as the volume of the wax is changed. In particular, the main valve is formed with a coolant hole.

CROSS-REFERENCE(S) TO RELATED APPLICATIONS

This application claims priority to and the benefit of Korean PatentApplication No. 10-2019-0017300, filed on Feb. 14, 2019, the entirecontents of which are incorporated herein by reference.

FIELD

Exemplary embodiments of the present disclosure relate to a thermostatconstituted in an engine cooling system to perform valve opening orclosing in response to temperature of coolant.

BACKGROUND

The statements in this section merely provide background informationrelated to the present disclosure and may not constitute prior art.

As illustrated in FIG. 1, a thermostat may be applied to an enginecooling system such that valve opening or closing thereof is controlledin response to a preset temperature of coolant.

In other words, the thermostat controls a bypass flow rate of thecoolant circulating into an engine and a flow rate of the coolant in aradiator.

A mechanical thermostat among such thermostats cannot perform variablecontrol considering conditions of the engine and environmental factorswhereas an electronic thermostat can control a flow rate of the coolantby controlling valve opening or closing in response to operatingconditions of the engine and the environmental factors.

In other words, the electronic thermostat, under high load condition,controls temperature of the coolant such that no problem in durabilityof the engine occurs whereas, under low load condition, it controlstemperature of the coolant to be high in consideration of fuelefficiency and performance of the engine.

Cooling modes in the engine cooling system may include an outletcontrolled cooling mode as shown in FIG. 1 and an inlet controlledcooling mode as shown in FIG. 2 depending on position of the thermostat.

Differential characteristics of the outlet controlled cooling mode andthe inlet controlled cooling method can be summarized as shown in thefollowing Table 1.

TABLE 1 Outlet Inlet controlled controlled Item cooling mode coolingmode 1) Follow-up to abrupt Disadvantage Advantage fluctuation incoolant (Hunting is remarkable, (Hunting is temperatureOvershoot/Undershoot is insignificant) remarkable) 2) Control of coolantDisadvantage Advantage temperature depending on engine load 3)Cavitation at high Advantage Disadvantage coolant temperature 4) Flowrate of coolant Not affected Not affected 5) Layout of cooling SimpleComplicated system (Being difficult to inject coolant) 6) Durability ofDisadvantage Advantage thermostat (Being liable to be affected byfluctuation of coolant pressure and temperature) 7) Operability of Notaffected by Affected by thermostat differential pressure of differentialcoolant pressure of coolant

As shown in Table 1, the outlet controlled cooling mode and the inletcontrolled cooling mode each have advantages and disadvantages.Particularly, in the case of the outlet controlled cooling mode, thereis a disadvantage in terms of abrupt fluctuation in coolant temperature.

Specifically, when coolant temperature rises in the engine, thethermostat is opened whereby the coolant circulates to the radiator. Atthis time, we have discovered that as the temperature of the coolant inthe radiator is low, high temperature coolant in the engine and lowtemperature coolant in the radiator are mixed with each other when thethermostat is opened at the initial stage and, resulting in abruptfluctuation in coolant temperature (i.e., overshoot/undershoot andhunting of the coolant) as shown in FIG. 3.

As a result, fluctuation in temperature of the coolant in an engine headand block, the radiator, a heater core, an oil cooler, an exhaust gasrecirculation (EGR) cooler and the like becomes large, durability ofboth the engine and the radiator may be deteriorated due to thermalshock of the engine.

Such thermal shock due to abrupt fluctuation in coolant temperature,which may be caused by valve opening/closing actuation of thethermostat, occurs in both mechanical and electronic thermostats.

The above information disclosed in this Background section is only forassisting understanding of the background of the disclosure and it maytherefore contain information that does not form the prior art that isalready known to those who have ordinary skill in the art.

SUMMARY

The present disclosure provides a thermostat for an engine coolingsystem, which is capable of reducing or minimizing occurrence of thermalshock which may be caused by abrupt fluctuation in coolant temperature.

Other objects and advantages of the present disclosure can be understoodby the following description and become apparent with reference to theembodiments of the present disclosure. Also, it is obvious to thoseskilled in the art to which the present disclosure pertains that theobjects and advantages of the present disclosure can be realized by themeans as claimed and combinations thereof.

In accordance with one aspect of the present disclosure, a thermostatfor an engine cooling system which is arranged between an engine and aradiator comprises: a housing having a coolant inlet through whichcoolant flows in from the engine and an outlet leading the coolant tothe radiator; and a main valve provided in the housing and coupled toone side of wax and configured to open or close the outlet as the volumeof the wax is changed. In particular, the main valve is formed with atleast one coolant hole.

Further, the thermostat may further comprise a bracket provided in thehousing and configured to support the main valve. In one form, thebracket may comprise an upper plate capable of contacting or beingseparated from the main valve to open or close the outlet leading to theradiator, and a stepped portion formed in an inner diameter portion ofthe upper plate may be arranged so as to abut against a part of the mainvalve.

More specifically, the at least one coolant hole of the main valve maybe arranged at a position to be abutted against the stepped portion.

Therefore, the at least one coolant hole is opened before the main valveopens the outlet leading to the radiator so that some of the coolantflows through the at least one coolant hole to the outlet leading to theradiator.

The at least one coolant hole may include a plurality of coolant holesformed through top and bottom surfaces of the main valve, and theplurality of coolant holes may be arranged along a peripheral portion ofthe main valve with predetermined intervals.

In one form, the thermostat may further comprise a bypass valveconfigured to open or close a bypass outlet formed in the housing, andthe bypass outlet is configured to guide the coolant coming through thecoolant inlet to the engine.

Further, the bypass valve may be configured to move in a direction ofclosing the bypass outlet when the at least one coolant hole is moved ina direction of being opened.

Further, the bypass valve may be configured to be connected to the waxby means of a shaft of the bypass valve to operate in conjunction withthe main valve.

Further, with this configuration, a flow path to the radiator is closedwhen the main valve is in contact with both the upper plate and thestepped portion; the flow path to the radiator is opened partially whenthe main valve is in contact with the upper plate and spaced apart fromthe stepped portion; and the flow path to the radiator is opened whenthe main valve is spaced apart from both the upper plate and the steppedportion.

It is to be understood that both the foregoing general description andthe following detailed description of the present disclosure areexemplary and explanatory and are intended to provide furtherexplanation of the disclosure as claimed.

Further areas of applicability will become apparent from the descriptionprovided herein. It should be understood that the description andspecific examples are intended for purposes of illustration only and arenot intended to limit the scope of the present disclosure.

DRAWINGS

In order that the disclosure may be well understood, there will now bedescribed various forms thereof, given by way of example, referencebeing made to the accompanying drawings, in which:

FIG. 1 is a schematic view of an example of an engine cooling system ofan outlet controlled cooling mode;

FIG. 2 is a schematic view of an example of an engine cooling system ofan inlet controlled cooling mode;

FIG. 3 is a graph for showing problems in an outlet controlled coolingmode;

FIG. 4 is a schematic diagram of an engine cooling system according toan embodiment of the present disclosure;

FIG. 5 is a schematic view of a thermostat for an engine cooling systemaccording to an embodiment of the present disclosure;

FIGS. 6A and 6B show examples of configuration of a thermostat accordingto an embodiment of the present disclosure respectively; and

FIGS. 7 and 8 illustrate operating states of a thermostat for an enginecooling system according to an embodiment of the present disclosurerespectively.

The drawings described herein are for illustration purposes only and arenot intended to limit the scope of the present disclosure in any way.

DETAILED DESCRIPTION

The following description is merely exemplary in nature and is notintended to limit the present disclosure, application, or uses. Itshould be understood that throughout the drawings, correspondingreference numerals indicate like or corresponding parts and features.

In order to fully understand the present disclosure, operationaladvantages of the present disclosure and objects achieved byimplementing the present disclosure, the accompanying drawingsexemplifying forms of the present disclosure and contents described inthe accompanying drawings need to be referred to.

In describing the exemplary forms, detailed description of technologyknown in the art or iterative description may be made shortly or omittedto avoid obscuring the subject matter of the present disclosure.

FIG. 4 is a schematic diagram of an engine cooling system according toan embodiment of the present disclosure and FIG. 5 is a schematic viewof a thermostat for an engine cooling system according to an embodimentof the present disclosure.

Hereinafter, the thermostat for an engine cooling system according tothe embodiment of the present disclosure will be described withreference to FIGS. 4 and 5.

The thermostat according to the embodiment of the present disclosure isprovided between an engine (head, block) and a radiator in an enginecooling system as shown in FIG. 4 to control valve opening or closing ofbypass lines leading to a heater and an exhaust gas recirculation (EGR)cooler, to a radiator and to an oil cooler depending on coolanttemperature and to control flow rate of coolant depending on openingdegree of a valve.

By using such control of flow rate of coolant, flow rate of the coolantcan be optimally controlled depending on characteristics, controlstrategy and operating conditions of the engine, so that engineperformance, fuel efficiency and cooling and heating performance can beimproved even by a simple configuration.

In addition, such control can be applied to an engine cooling system ofan outlet controlled cooling mode in which a thermostat is provided atan outlet side of the engine, in order to prevent thermal shock due toabrupt fluctuation in temperature of the coolant, which may be causedbecause high temperature coolant passed through the engine and lowtemperature coolant from a radiator are mixed with each other.

To this end, the thermostat according to the embodiment of the presentdisclosure is arranged in a flow path between the engine (engine headand engine block) and the radiator and configured such that a valvesupported by a bracket 170 is operated as the volume of wax 120 in ahousing 110 is changed. The valve controls the path and flow rate ofcoolant.

The housing 110 is formed with a coolant inlet 111, a bypass outlet 112and an outlet 113 leading to the radiator.

In addition, a main valve 130 and a bypass valve 140 are provided tocontrol opening/closing and flow rate of the outlet 113 leading to theradiator and the bypass outlet 112, respectively.

The main valve 130 is arranged to be coupled to a piston 150 so as toopen or close the outlet 113 leading to the radiator. This main valve isshifted at the top of the piston 150 by means of change in volume of thewax 120 in the bracket 170 and in turn open or close the outlet 113guiding the coolant to the radiator. Then, after shifting the position,the main valve is returned elastically to its original position by meansof a main valve spring 161 of which one side is coupled to the mainvalve 130 and the other side is supported in the bracket 170.

Further, a bypass valve 140 is coupled to the other side of the wax 120.

The bypass valve 140 is provided at the bypass outlet 112 side andcoupled to the wax 120 by means of a shaft 141 of the bypass valve toopen or close the bypass outlet 112.

Accordingly, the bypass valve is shifted by means of change in volume ofthe wax 120. Then, after shifting the position, the bypass valve isreturned elastically to its original position by means of a bypass valvespring 162 of which one side is coupled to the bypass valve 140 and theother side is coupled to the wax 120.

In this way, the main valve 130 and the bypass valve 132 are operated tobe opened or closed in conjunction with each other by means of change involume of the wax 120.

Further, a sensor 180 for measuring temperature of the coolant may beprovided at the coolant inlet 111 to control the coolant.

In this way, when the volume of the wax 120 is changed as shown in FIG.7, the bypass valve 140 closes the bypass outlet 112 and the main valve130 is operated to supply the coolant from the coolant inlet 111 to theoutlet 113 leading to the radiator.

Furthermore, this embodiment of the present disclosure employs a meansfor preventing abrupt fluctuation in temperature due to mixing of hightemperature coolant at the coolant inlet 111 side and low temperaturecoolant at the outlet 113 side leading to the radiator.

Specifically, an upper plate 171 of the bracket 170, which abuts againstthe main valve 130 to close the flow path or is separated from the mainvalve 130 to open the flow path, is provided at its inner diameterportion with a stepped portion 171-1 wherein the stepped portion 171-1and the main valve 130 are to be arranged in such a manner that thestepped portion covers a part of a peripheral portion of the main valve130.

Further, the main valve 130 is formed with a coolant hole 131. In oneform the coolant hole 131 is formed through top and bottom surfaces ofthe main valve 130.

Accordingly, when the main valve 130 is shifted downward as shown inFIG. 7, side ends of the main valve 130 abut against the upper plate 171so that the coolant cannot pass through the peripheral portion of themain valve 130, whereas the top face of the main valve is separated fromthe stepped portion 171-1 so that the outlet 113 leading to the radiatoris partially opened and thus only a small amount of the coolant can passthrough the coolant hole 131 formed in the main valve 130.

This embodiment of the present disclosure is configured such that themain valve 130 is not completely opened for a moment but the coolanthole 131 formed in the main valve 130 is first opened, thereby allowingonly a small amount of flow rate of the coolant to flow through theoutlet 113 leading to the radiator.

Accordingly, cold coolant is less circulated when the thermostat isopened at the initial stage. As a result, engine warm up is faster sothat fuel efficiency is improved. In addition, there is no abruptthermal shock (overshoot/undershoot and hunting) in temperature of thecoolant of the engine and the radiator so that thermal durability of theengine is improved.

Moreover, when the main valve 130 is further shifted downward than thatshown in FIG. 7, as shown in FIG. 8, the main valve 130 is separatedfrom both the upper plate 171 and the stepped portion 171-1. As aresult, the outlet 113 leading to the radiator is completely openedwhereby the coolant is allowed to flow through the outlet 113 leading tothe radiator via the coolant hole 131 formed in the main valve 130 andthe flow path between the side face of the main valve 130 and the upperplate 171.

The coolant hole 131 is formed in a portion of the main valve 130 whichis covered by the stepped portion of the upper plate 171. In addition,the coolant hole may be implemented in various ways.

As a way of example, the coolant hole 131 may be a plurality of coolantholes 131-1 having a circular shape in a plane section wherein the holesare spaced from each other at equal intervals or predetermined intervalsand positioned at the same radial distance, as shown in FIG. 6A.

Alternatively, each hole may be formed in a shape of the hole 131-2which is formed by perforating a partial section of the main valveirregularly, as shown in FIG. 6B.

According to the thermostat for the engine cooling system of the presentdisclosure, initial flow rate of the coolant in the thermostat isprecisely controlled so that thermal shock by coolant, which may becaused by initial uncontrolled opening of the thermostat, can beprevented.

In addition, cold coolant less circulates when the thermostat is openedat the initial stage and as a result, engine warm up is faster so thatfuel efficiency can be improved.

Therefore, abrupt thermal shock (overshoot/undershoot and hunting) bycoolant is prevented from occurring in the head and block, etc. of theengine so that thermal durability of the engine and the radiator isimproved.

Further, durability and reliability of the engine can be improved inthat thermal shock by coolant, which may be caused by initialuncontrolled opening of the thermostat and ultimately affects theradiator, the heater core, the oil cooler, the EGR cooler and the like,is prevented and thus excessive fluctuation in temperature is prevented.

Although the present disclosure has been described in the foregoing withreference to the drawings illustrated by way of an example, the presentdisclosure is not limited to the disclosed embodiments and it isapparent to those of ordinary skill in the art that variousmodifications and variations can be made to the present disclosurewithout departing from the spirit and scope of the disclosure.

What is claimed is:
 1. A thermostat for an engine cooling system, whichis arranged between an engine and a radiator, comprising: a housinghaving a coolant inlet through which coolant flows in from the engineand an outlet leading the coolant to the radiator; and a main valveprovided in the housing and coupled to one side of wax and configured toopen or close the outlet as a volume of the wax is changed, wherein themain valve is formed with at least one coolant hole.
 2. The thermostataccording to claim 1, further comprising a bracket provided in thehousing and configured to support the main valve, wherein the bracketcomprises an upper plate configured to contact or be separated from themain valve so as to open or close the outlet leading, and a steppedportion formed in an inner diameter portion of the upper plate isarranged so as to abut against a part of the main valve.
 3. Thethermostat according to claim 2, wherein the at least one coolant holeof the main valve is arranged at a position to be abutted against thestepped portion.
 4. The thermostat according to claim 2, wherein the atleast one coolant hole is opened before the main valve opens the outletleading to the radiator such that some of the coolant flows through theat least one coolant hole to the outlet leading to the radiator.
 5. Thethermostat according to claim 2, wherein the at least one coolant holecomprises a plurality of coolant holes formed through top and bottomsurfaces of the main valve, and the plurality of coolant holes arearranged along a peripheral portion of the main valve with predeterminedintervals.
 6. The thermostat according to claim 2, further comprising: abypass valve configured to open or close a bypass outlet formed in thehousing, the bypass outlet configured to guide the coolant comingthrough the coolant inlet to the engine.
 7. The thermostat according toclaim 6, wherein the bypass valve is configured to move in a directionof closing the bypass outlet when the at least one coolant hole is movedin a direction of being opened.
 8. The thermostat according to claim 6,wherein the bypass valve is configured to be connected to the wax by ashaft of the bypass valve to operate with the main valve.
 9. Thethermostat according to claim 2, wherein a flow path to the radiator isclosed when the main valve is in contact with both the upper plate andthe stepped portion; the flow path to the radiator is opened partiallywhen the main valve is in contact with the upper plate and spaced apartfrom the stepped portion; and the flow path to the radiator is openedwhen the main valve is spaced apart from both the upper plate and thestepped portion.